Anki - Anki is a program which makes remembering things easy. Because it's a lot more efficient than traditional study methods, you can either greatly decrease your time spent studying, or greatly increase the amount you learn.

Duolingo - Duolingo is a free language learning app for iOS, Windows and Android devices. The app makes learning a new language fun by breaking learning into small lessons where you can earn points and move up through the levels. Read more about Duolingo.

Kanji Book - Learn Japanese online with kanji mnemonics. Study all of the jōyō kanji with the best spaced repetition system. It's easier and better than any flashcard app.

Zorbi - Spaced-Repetition Flashcards - Other tools are built by boomers, Zorbi is built by students.

Repetitions - Repetitions is a cross-platform spaced repetition system (SRS), an intelligent flashcard application that makes learning and memorization easy.

SmartCards+ - Spaced Repetition Software for iOS. Modern, powerful and easy to use.